MEIOTIC BEHAVIOR OF SEX-CHROMOSOMES INVESTIGATED BY 3-COLOR FISH ON 35142 SPERM NUCLEI FROM 2 47,XYY MALES

Meiotic segregation of sex chromosomes from two fertile 47,XYY men was analysed by a three-colour fluorescence in situ hybridisation procedu re. This method allows the identification of hyperhaploidies (spermato zoa with 24 chromosomes) and diploidies (spermatozoa with 46 chromosom es), and their meiotic origin (meiosis I or II). Alpha-satellite probe s specific for chromosomes X, Y and 1 were observed simultaneously in 35142 sperm nuclei. For both 47,XYY men (24 315 sperm nuclei analysed from one male and 10 827 from the other one) the sex ratio differs fro m the expected 1:1 ratio (P < 0.001). The rates of disomic Y, diploid YY and diploid XY spermatozoa were increased for both 47,XYY men compa red with control sperm (142050 sperm nuclei analysed from five control men), whereas the rates of hyperhaploidy XY, disomy X and disomy 1 we re not significantly different from those of control sperm. These resu lts support the hypothesis that the extra Y chromosome is lost before meiosis with a proliferative advantage of the resulting 46,XY germ cel ls. Our observations also suggest that a few primary spermatocytes wit h two Y chromosomes are able to progress through meiosis and to produc e Y-bearing sperm cells. A theoretical pairing of the three gonosomes in primary spermatocytes with an extra sex chromosome, compatible with active spermatogenesis, is proposed.